Reproductive patterns and effective pollen dispersal were investigated in a Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) clonal seed orchard using 11 isozyme loci as genetic markers.Progenies from 94 mother trees were analysed by the mixed-mating and the neighbourhood models and outcrossing rates were estimated as 0.96 and 0.97, respectively. The proportion of offspring resulting from pollination by males located outside the neighbourhood of each mother tree (30 m in radius) was estimated as 0.54, with 43 per cent of matings resulting from outcrossing with nearby males (within neighbourhoods). The effects of distance and direction of individual males from mother trees, pollen fecundity and phenological synchronization were all significant in determining outcross mating patterns within neighbourhoods. Generally, male reproductive success increased with proximity and phenology overlap with mother tree and pollen fecundity. The effect of different factors influencing male reproductive success varied among the three groups of mother trees divided according to the time of female receptivity (early, intermediate and late). Phenology was important in the early and intermediate groups whereas fecundity was important in the intermediate and late phenology groups. Both distance and directionality effects were significant in the early and late classes. The directionality effect could be partially explained by the wind patterns existing during the pollination period. The mean effective number of males mating with each female within neighbourhoods was 10.95 (49.31 per cent of males within neighbourhoods).Keywords: mating system, neighbourhood model, pollen dispersal, Pseudotsuga menziesii, reproductive success. IntroductionThe mating system plays a central role in determining the genetic structure of plants. Patterns of pollen dispersal, gene flow between populations and differential reproductive success influence the levels of inbreeding, as well as effective population size and distribution of genetic diversity between and within populations. In addition to their importance to population genetics theory, mating patterns are also of great practical value in agriculture and forestry (Adams & Birkes, 1991;Snow & Lewis, 1993 species and it is expected that several factors, including distance, fecundity and flowering phenology, may affect individual reproductive success and patterns of pollen dispersal (Broyles & Wyatt, 1991;Adams et aL, 1992b;Devlin et a!., 1992;Snow & Lewis, 1993;Burczyk et a!., 1996). For theoretical and practical reasons it is important to identify these factors and the best way to achieve this is the application of genetic estimation techniques using selectively neutral genetic markers (Smouse & Meagher, 1994). Apparently, if an effect of a possible factor influencing reproductive success is to be calculated from individual fertilities, paternity methods are not very suitable for determining its significance if exclusion probabilities are not very high (Devlin et al., 1988;Adams et al., 1992b). Other...

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-Genetic variation has been assessed in 73 (mostly French) populations of the wild service tree (Sorbus torminalis) using 15 isozymes loci. In spite of a relatively high coefficient of genetic differentiation among populations (F ST = 15%), only a weak geographical structure was detected. This may be explained by the small size and young age of the populations due to the importance of founder effects, combined with the high levels of seed flow among populations. These features are typical of species characterised by metapopulation dynamics.genetic diversity / differentiation / metapopulation / Rosaceae / spatial structure Résumé -Variabilité génétique d'une espèce forestière disséminée : Sorbus torminalis L. (Crantz). De nombreuses études se sont intéressées à la diversité génétique des plantes rares, menacées de disparition, ou à celles largement répandues qui présentent un grand intérêt économique. Par contre, le cas des espèces ayant une aire de répartition importante mais présentant des densités faibles reste peu abordé, en particulier chez les arbres forestiers. Dans les forêts tempérées, les arbres forestiers disséminés occupent une place secondaire. L'alisier torminal (Sorbus torminalis) est une espèce fruitière disséminée au comportement post-pionnier nomade. Ses graines sont dispersées par les oiseaux. 67 populations françaises et 6 populations d'Europe centrale ont été étudiées à l'aide des isozymes. Une forte différentiation entre populations a été trouvée (F ST = 15 %), combinée à une faible structuration géographique. Ceci peut s'expliquer par les effets de fondation importants liés au comportement écologique de l'espèce, et aux flux de graines entre populations éloignées, liés à la dissémination par des oiseaux. Le modèle en métapopulation, avec des populations subissant des phé-nomènes de colonisation et d'extinction, mais restant interconnectées par des flux de gènes, semble particulièrement bien s'appliquer à cette espèce. Au vu de ces résultats, une gestion permettant l'implantation de l'alisier dans de nouveaux sites pouvant recevoir des flux de gènes des populations préexistantes doit être encouragée.Rosaceae / diversité génétique / métapopulation / differentiation / structure spatiale

Based on an F(1) progeny of 73 individuals, two parental maps were constructed according to the double pseudo-test cross strategy. The paternal map contained 16 linkage groups for a total genetic length of 1,792 cM. The maternal map covered 1,920 cM, and consisted of 12 linkage groups. These parental maps were then integrated using 66 intercross markers. The resulting consensus map covered 2,035 cM and included 755 markers (661 AFLPs, 74 SSRs, 18 ESTPs, the 5S rDNA and the early cone formation trait) on 12 linkage groups, reflecting the haploid number of chromosomes of Picea abies. The average spacing between two adjacent markers was 2.6 cM. The presence of 39 of the SSR and/or ESTP markers from this consensus map on other published maps of different Picea and Pinus species allowed us to establish partial linkage group homologies across three P. abies maps (up to five common markers per linkage group). This first saturated linkage map of P. abies could be therefore used as a support for developing comparative genome mapping in conifers.